Refining lead



Patented Dec. 15, 1925.

PHILIP W. DAVIS, 01 CAMBRIDGE, MASSACHUSETTS.

BEFIN ING LEAD.

No Drawing.

To all whom it may concem:

Be it known that I, PHILIP W. DAVIS, a

' citizen of the United States, residing at Cambridge, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements in Refining Lead; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in, the art to which it appertains to make and use the same.

The present invention relates to an improvement in refining lead.

Considerable quantities of storage battery plate lead finds its way to the markets and requires refining before it is available for reuse in the arts. .The mere removal of foreign matter from the lead antimony alloy of which these plates are principally formed produces a marketable product but if a substantial portion of the lead could be recovered in a pure state as soft lead a much wider market would be obtained and better prices secured for the product of the refining process. I

One object of this invention is to refine storage battery plate lead in order to produce as much soft lead as possible from the alloy, the remainder being available for the market as a high antimony lead alloy. The invention in its broader aspects ma be used for removing various alloy metals rom lead alloys or for recovering pure lead from various alloys of lead. It may further be used for refining new lead as well as for refining old lead. Other features of the invention will be pointed out in this specification.

The process broadly stated consists in exposing molten lead alloy to the action of molten litharge under conditions of agitation so that the molten lead alloy is brought into intimate contact with the refinmg molten litharge.

The invention consists in the method of refining lead hereinafter described and particularly defined in the claims.

In describing the process, the specific method of refinin lead from old storage battery plates wil? first be described.

The fundamental feature of the present invention consists in exposing molten lead alloys to intimate contact with molten litharge in bodies of small dimensions. This operation is performed in a rotary furnace;

Application filed May 14, 1925. Serial No. 30,354.

that is to say, in a furnace which consists of a shell rotated by power and lined with magnesite or other basic lining material. i

The exposed surface of the lining is'roughened so as thereby to afford a convenient means of agitating the contents of the furnace. At one end of the furnace the lead alloy in molten condition will be introduced, and at the other end of the furnace molten litharge will be introduced. The amount of lead alloy introduced at the one end will be such as toform a thin layer of this material in molten condition in the furnace and over it will float the molten litharge. Preferably the lead alloy will be caused to flow in one direction through the furnace and the molten litharge will be caused to flow in the opposite direction. This has substantial advantages because the lead bearing the least amount of antimony will be exposed to the action of the molten litharge when it is first introduced and is therefore most active; then as the two streams of molten materials flow, in a condition of more or less agitation, in opposite directions in contact with each other, the litharge rapidly takes up the antimony content of the alloy and, as. the other end of the furnace is approached the incoming lead antimony alloy of highest antimony content is exposed to the action of the less active litharge. The litharge product, probably lead antimoniate, is discharged at one end by overflowing the end of the furnace, a suitable lip being provided and the molten lead is discharged at the other end, a dam being provided to prevent the molten litharge from flowing out at that end. The interior of the furnace is heated by an oil burner to maintain the temperature at proper condition for the reaction. The furnace will be rotated at a convenient rate of speed. A furnace 4 feet long and 16 inches in diameter in which the rotations are from one to six turns per minute has been employed. The rotation of the furnace conduces to the successful performance of the operation, because on the rising side of the furnace as the metal is lifted up by the turnin of the furnace the alloy beingrefined is a lowed to roll or fall back through the molten litharge, thereby bringing the materials into intimate contact and conducing to the oxidation of the antimony content of the lead. The rotation furthermore has the advantage of preserving the lining of the furnace and heating that portion of the lining to which the molten materials are exposed, for it is apparent that Where the lining is heated by direct exposure to a flame and then carried 'under the molten materials the latter are kept in a state of agitation and are better heated than where the material is quiescent or a slowly flowing body.

\Vhile the use of the rotating furnace is to be preferred for the reasons hereinbefore stated, the use of such apparatus is not essential to the practicing of the invention, as it may be practiced by the use of a stationary furnace. In such case the preferred method of performing the operation, would, as before, involve the counter-current feeding of molten litharge and molten alloy to the opposite ends or sides of the furnace through or across which the streams would flow in counter-current fashion with respect to each other and discharge from opposite ends or sides. Thus the alloy might flow in at one side and the soft lead be discharged at the opposite side; at the latter side the molten litharge wouldbe introduced which would "flow counter-current to the alloy and be discharged as a lead antimoniate upon the side where the alloy was being introduced.

The invention is not limited to countercurrent operation, as it may be performed in a stationary furnace wherein the molten litharge and lead alloy are maintained in heated and agitated condition in order to bring the lead' alloy into intimate contact with the litharge for the purpose of removing the alloy metals from the material being refined. The important requisite of the process is the intimate mixture of the molten lead alloy with molten litharge so that all portions of the alloy are brought in contact with the molten litharge so as thereby to remove from the lead alloy the alloy metals by oxidation thereof.

One important use of the invention con templates the refining of old storage battery plates because of the very considerable quantity of such material available and the greatly extended market for a pure lead and a lead antimony alloy of high antimony percentage.

The lead antimony product of the process may be reduced in any suitable manner to recover an alloy which contains a large percentage of antimony.

While this method is particularly desirable for use in refining the lead from storage battery plates, it is within the contemplation of the invention to employ it in refining the lead from the smelters whichv contain antimony, or for that matter other metals, and the gist of the invention resides in exposing lead alloys to the action of molten litharge under such conditions of massacre agitation as to cause an intimate contact of the molten materials with each other. The most important aspect of the invention is found in exposing the lead alloy and the molten litharge to each other in thin moving layers.

An important feature of the invention is found in its use as a continuous process, lead alloy being continuously introduced and the refined lead deprived of its alloy metals being continuously drawn off as one product of the process.

One feature of the invention resides in the production of the litharge used in the refining of the alloy in the working of the process itself. As the alloy makes its way through the furnace it is first gradually deprived of its alloy metals but while at the completion of this refining, process it is practically free from such alloy metals, it contains entrained oxides. In a second portion of the furnace conveniently called the refining chamber the metal is subjected to air blasts or jets and the oxides may thus be removed by the air. This pool of metal will preferably be separated from the remainder of the metal so that the violent agitation thereof by the air will not extend into the body of the pool of metal in the other portion of the furnace where the removal of the alloy metals is taking place and which may conveniently be termed the reaction chamber.( The separation of the two chambers may be effected by the use of a low dam extending slightly above the surface of the lead but not as high as the top of the litharge, and having openings below for the free passage of the lead therethrough. In this refining pool the entrained oxides will be removed and co-incident with their removal an amount of lead will be oxidized to form litharge. material brought to the surface by this air blowing process and floating on the surface of the pool will be more or less frothy owing to the agitation of the pool by the air currents and will be here further oxidized into litharge. This body of litharge and removed oxides accumulates and fiows continuously over the dam into the refining end or chamber of the furnace where it will subject the leadto the refining operation hereinbefore described. A s ecial flame will be employed in the re ning chamber under conditions of operation requiring addition of heat to maintain the htharge formed on the surface of the lead in a molten condition.

The oxidation of the lead to form the litharge is more readily accomplished where the lead is soft, that is after it has been deprived of the alloy metals, as their presence retards lead oxidation. In the process, therefore, as carried on in this manner, the se aration of the alloy metals and the oxidation The.

of the lead to form lithar e are accomplished under favorable con itions.

Instead of formin the lithar e in the refining chamber ad acent to t e reaction chamber, the refining chamber may be used to remove the entrained oxides by simple agitation. Or, if desired, the lead from the reaction chamber may be delivered to a separate furnace, where the entrained oxides may be removed and the litharge formed.

Important advantages flowing from the use of this method reside in the reduction of investment inplant required for its operation, and in labor required in carrying it on.

Whereas in refining lead in large masses by the various methods heretofore practiced by the use of reverberatory furnaces, the operation required a certain length of time, it is tobe noted that in the present method the exposure of the alloy to the refining influence of the litharge in thin layers or bodies of small dimensions, resulting in intimate contacts between them, enormously speeds up the rate of reaction.

It will be observed that this method of making the litharge directly in the furnace in which'it is employed conduces to the simplicity of the refining o eration, as it avoids the use of a separate urnace in which to melt the litharge.

Having thus described the invention, what is claimed is:

1. The method of refining lead which consists in exposing lead alloys in molten condition to the action of molten-litharge by causing the two materials to be exposed to each other in bodies of small dimensions.

2. The method of removing alloy metals from lead which. consists in exposing the molten'alloy metal to the action of molten litharge. in thin layers.

3. The method of removing alloy metal from lead which consists in exposing the molten lead alloy to molten litharge in counter-current fashion so that the alloy metal first exposed to the -molten litharge contains least alloy metals and that last exposed to the molten litharge is richest in al- 10y metals.

4. The continuous method of removing alloy metals from lead which consists in the exposure of molten lead allo flowing in one certain direction in a smal and agitated stream to the action of a continuous stream of molten litharge flowing counter-currentwise to the lead alloy in a contacting agitated stream.

5. The continuous method of removing alloy metals from lead alloy which consists in causing a stream of molten lead alloy to flow in one direction through a heated furnace and'in causing a current of molten litharge to flow over the molten lead alloy through the furnace in the-opposite direction superposed upon the stream of lead alloy.

6. The continuous method of removing alloy metals from lead which consists in causing two agitated streams ofmolten alloy and litharge to flow through a furnace in contact with each other in the furnace.

In testimony whereof I have signed my name to this specification.

PHILIP W. DAVIS. 

